A small size refrigerant apparatus used for an automotive air-conditioner has no lubricant reserver by request for miniaturizing and lightening a compressor. The refrigerant apparatus employs circulating lubrication method, wherein the lubricant circulates with refrigerant within the refrigerant passage and returns to the compressor so as to lubricate the compressor.
When the lubricant stays at a region other than compressor an amount of returned lubricant to the compressor reduces and lubrication of the compressor may be insufficient. It is required to keep circulation of the lubricant within the refrigerant passage so as to improve reliability and durability of the compressor. Japanese utility model laid open No. 62-195052 shows a method to keep circulating lubrication wherein one compressor distributes refrigerant to plurality of evaporators. When the refrigerant is not supplied to one of evaporators, the lubricant tends to stay near a junction of a refrigerant return pipe between each evaporator and the compressor. Such problem is solved by inclining return pipe downward from each evaporator near the junction of the return pipe. When the amount of circulating lubricant is increased in a circulating lubrication method, the amount of circulating refrigerant is relatively decreased and coefficient of heat transmission in a condenser and an evaporator falls off so that a refrigerating capacity falls off and consumptive power increases.
Thus, as a recent tendency, the circulating amount of lubricant is getting as small as possible. As the utility model laid-open states, lubricant adheres inside of the refrigerant passage, particularly of a low pressure refrigerant passage at the downstream of an expansion valve. When a load of a refrigerant apparatus reducing the amount of circulating lubricant is decreased, amount of returned lubricant to the compressor decreases, so that there is possibility to occur a shortage of lubricant in the compressor.
In the apparatus shown in the utility model laid open, lubricant is prevented from staying near the junction of the refrigerant return pipe in case of using plural evaporators. The apparatus, however, can not solve the problem of adhesion of lubricant to the inside wall of the low pressure refrigerant passage.
To solve the above problem, it is supported that the whole of the low pressure refrigerant passage is inclined toward an inlet of the compressor, but is is not practical to realize. It is possible to employ lubricant supplying methods other than circulating lubrication method, however, the lubricant supplying methods requires drastic change of the construction and is against the requirement of miniaturizing and lightening the refrigerant apparatus.